RIO DE JANEIRO (Reuters) - Brazilian authorities investigating the assassination of a Rio de Janeiro councilwoman are closing in on suspects, including a fellow councilman accused of links to paramilitary militias, two sources with knowledge of the investigation told Reuters on Wednesday.

Pictures of Rio de Janeiro city councilor Marielle Franco are seen, where she was shot dead in Rio de Janeiro, Brazil May 9, 2018. REUTERS/Ricardo Moraes

Marielle Franco, an outspoken critic of the militias that control many impoverished areas of Brazil’s second-largest city, was shot four times in the head in March as she rode in a car in central Rio. Her driver was also killed.

The killing sparked major protests in Brazil and demands that her murder be solved quickly. As a rare black politician who came from a poor background, she was seen by many of Rio’s impoverished as a hope that their voices would increasingly be heard.

O Globo newspaper reported on Tuesday night that in relation to Franco’s murder police were investigating councilman Marcello Siciliano, whose political stronghold is an area in western Rio controlled by militias.

Two government sources confirmed to Reuters that investigators were close to naming suspects and that Siciliano is one of those involved, citing evidence given by a militia member. The sources spoke on condition their names not be used, saying they were not authorized to discuss the case.

Siciliano strongly denied any link to the case in a written statement released on Wednesday and sent to Reuters, calling the allegations “totally false.”

At a media conference later Wednesday, Siciliano underscored his innocence, saying that he had a good relationship with Franco and that “she had even attended my birthday party.”

He said he had already been questioned by police, as have several councilmen who knew Franco, and that he was available to answer any questions investigators might have at any time.

“Now, more than ever, I ask that everything be brought to light as quickly as possible,” Siciliano said.

The two sources told Reuters that a militia member who is cooperating with federal police told authorities he witnessed four meetings last year between Siciliano and former police officer Orlando Oliveira de Araujo, during which they plotted Franco’s murder.

Araujo was jailed in October while prosecutors investigate a murder charge and allegations that he led a militia in western Rio. His lawyer did not return a request for comment.

Militias, formed by former and current police officers, firefighters, prison guards and even members of the military, have rapidly expanded in the past decade.

They control black-market transport, water and cooking gas sales, extort small businesses for “protection” and are increasingly involved in the drug trade, among other illegal activities.

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“There is no doubt that this crime was committed by members of a militia,” one of the sources told Reuters. “Marielle had been getting in the way of militia plans and activities.”

Franco, 38, was a rising star in the Socialism and Liberty Party (PSOL). She was born and raised in a slum, was a strong advocate for the poor and denounced brutal policing tactics used in shantytowns, where hundreds are killed each year in the crossfire between police and drug gangs who control most of Rio’s slums.

Political violence is common in Brazil. In the months before the 2016 city council elections in Baixada Fluminense - a hardscrabble region that surrounds Rio - at least 13 politicians or candidates were murdered before ballots were cast.